Floating-Point Status and Control Register, Fpscr, Dnm | ARM r1p3

FPU Programmer’s Model

12.3.2Floating-Point Status and Control Register, FPSCR

FPSCR is a read/write register that can be accessed in both Privileged and nonprivileged modes. All bits described as DNM in Figure 12-3are reserved for future expansion. These bits must be initialized to zeros. To ensure that these bits are not modified, any code other than initialization code must use read-modify-write techniques when writing to FPSCR. Failure to observe this rule can cause Unpredictable results in future systems.

Figure 12-3shows the bit arrangement of the FPSCR Register.

31 30 29 28 27 26 25 24 23 22 21 20 19 18 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

N Z C V

QC

DNM

DN

FZ

RMODE

STRIDE

DNM

LEN

DNM

DNM

IDE

IXC

IXE

UFC

UFE

OFC

OFE

DZC

DZE

IOC

IOE

IDC

			Figure 12-3 Floating-Point Status and Control Register format
	Table 12-4shows how the bit values correspond with the FPSCR Register functions.
			Table 12-4 FPSCR Register bit functions

	Bits	Field	Function

[31]		N	Set if comparison produces a less than result, resets to zero

[30]		Z	Set if comparison produces an equal result, resets to zero

[29]		C	Set if comparison produces an equal, greater than, or unordered result, resets to zero

[28]		V	Set if comparison produces an unordered result, resets to zero

[27]		QC	Do Not Modify (DNM)/Read As Zero (RAZ)

[26]		DNM	DNM

[25]		DN	Default NaN mode enable bit:
			0 = default NaN mode disabled, this is the reset value
			1 = default NaN mode enabled.

[24]		FZ	Flush-to-zero mode enable bit:
			0 = flush-to-zero mode disabled, this is the reset value
			1 = flush-to-zero mode enabled.

[23:22]		RMODE	Rounding mode control field:
			b00 = round to nearest (RN) mode, this is the reset value
			b01 = round towards plus infinity (RP) mode
			b10 = round towards minus infinity (RM) mode
			b11 = round towards zero (RZ) mode.

[21:20]		STRIDE	Indicates the vector stride, reset value is 0x0

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ARM r1p3, R4F manual Floating-Point Status and Control Register, Fpscr, Fpscr Register bit functions, Dnm, Rmode, Stride

Contents

Cortex-R4 and Cortex-R4F Copyright 2009 ARM Limited. All rights reserved Cortex-R4 and Cortex-R4FTechnical Reference Manual Chapter Introduction Cortex-R4 and Cortex-R4F Technical Reference Manual Chapter Processor Initialization, Resets, and Clocking Chapter AC Characteristics Appendix B ECC Schemes List of Tables Adfsr and Aifsr bit functions Dirty register format, with ECC 11-12 Example interlocks 14-11 Table A-18 FPU signals Table C-1 List of Figures Cache operations C7 format for Set and Way Vector Catch Register format 11-20 Feedback on Preface Identifies the major revision of the product Using this bookAbout this book Product revision status Typographical Conventions Signals Timing diagrams Other publications Further readingThis section lists publications by ARM and by third parties ARM publications Feedback on this book FeedbackARM welcomes feedback on this product and its documentation Feedback on this product Introduction About the processor About the architecture System control coprocessor on Interrupt handling on Components of the processorThis section describes the main components of the processor Debug on Prefetch unit Data Processing UnitFloating Point Unit Load/store unit TCM interfaces Instruction and data cachesMemory Protection Unit AXI slave interface Error correction and detection5 L2 AXI interfaces AXI master interface Real-time debug facilities DebugSystem performance monitoring ETM interface Low interrupt latency System control coprocessorInterrupt handling VIC port Changes Return from exception using data from the stack APB Debug interface Processor has the following interfaces for external accessExternal interfaces of the processor APB Debug interface ETM interface Test interface Shutdown mode Power managementRun mode Standby mode Atcm Configurable optionsConfigurable options MPU BtcmVFP FPU includeda B1TCMPCEN Configurable options at reset Feature Options RegisterAtcmpcen B0TCMPCEN Atcmrmw AtcmecenB0TCMECEN B1TCMECEN Instruction decode Execution pipeline stagesNames of the pipeline stages and their functions are Write-back of data from the execution pipelines First stage of data memory accessIss Execute stages Redundant core comparison Test features Design flow Product documentation, design flow, and architectureDocumentation Architectural information Build configurationConfiguration inputs Software configuration Advanced Microcontroller Bus Architecture protocol Processor identification Product revision information Revision field, Debug ID Register Variant field, Main ID RegisterRevision field, Main ID Register Variant field, Debug ID Register Exceptions on Programmer’s ModelRegisters on Program status registers on About the programmer’s model Thumb state Switching stateInstruction set states ARM state Operating modes Data types Little-endian format Memory formatsByte-invariantbig-endian format Little-endian format Byte-invariant big-endian format Register set Registers Register mode identifiers Mode Mode identifier General registers and program counter N, Z, C, and V bits Program status registers IT bits Q bit GE bits J bitDNM bits Non-maskable fast interrupts on E bitA bit I and F bits Modification of PSR bits by MSR instructions PSR mode bit valuesM40 Mode Visible state registers Thumb M bits ARM DDI 0363E Exception entry and exit summary Reset on Interrupts on Aborts onExceptions Exception entry and exit summary Leaving an exception Taking an exception Interrupt request ResetInterrupts Non-maskable fast interrupts Fast interrupt requestProgram status registers on Non-maskable fast interrupts Interrupt controller Interrupt entry flowchart Interrupt entry sequence Precise aborts AbortsPrefetch aborts Data aborts Aborts in Strongly Ordered and Device memory Imprecise aborts Supervisor call instruction Abort handler Breakpoint instruction Undefined instruction Exception vectors Acceleration of execution environments Architecture Reference Manual Unaligned and mixed-endian data access support Big-endian instruction support Initialization on Processor Initialization, Resets, and ClockingResets on Reset modes on 2 CRS InitializationCaches on TCM on 1 MPU Preloading TCMs Caches5 TCM Preloading TCMs with parity or ECC DMA into TCMWrite to TCM directly from debugger Using TCMs from reset NSYSPORESET ResetsNRESET PRESETDBGn Power-on reset Reset modes Halt operation Processor resetNormal operation Clock gating ClockingAXI interface clocking Clock gating AXI interface clocking System Control Coprocessor System control coprocessor functional groups About the system control coprocessor Fcse PID System control coprocessor register functionsFunction Register/operation Reference to description System performance Performance monitoring System control and configurationConfiguration Region TCM control TCM Status Cache control and configuration MPU control and configuration System performance monitor TCM control and configuration System performance monitor registers System validation ARM DDI 0363E RAZ System control coprocessor registersRegister allocation Number Enable Undefined MPU Region Access Read/writeUndefined MPU Region Size Read/write Control Undefined MPU Memory Region Read/write ARM DDI 0363E Count Undefined Undefined C3-c11 C12 Performance Monitor Read/writeEvent Select Read/write Unpredictable Performance Monitor Writes Context ID Read/write C14 User Enable Read/writeUndefined C1-c15 C12 C0-c15 C13 RAZ,ignore 7shows the arrangement of bits in the register 2 c0, Main ID Register Bits Field Function 3 c0, Cache Type RegisterMain ID Register bit functions TCM Type Register bit functions Bits Field Function To access the Cache Type Register, read CP15 with4 c0, TCM Type Register Cache Type Register bit functions Bits Field Function TCM Type Register bit functions To access the TCM Type Register, read CP15 withTo access the MPU Type Register, read CP15 with 5 c0, MPU Type Register 6 c0, Multiprocessor ID Register Processor Feature RegistersC0, Processor Feature Register 0, PFR0 Processor Feature Register 1 bit functions To access the Processor Feature Register 0 read CP15 withC0, Processor Feature Register 1, PFR1 Processor Feature Register 0 bit functions 3124 Reserved To access the Processor Feature Register 1 read CP15 with8 c0, Debug Feature Register Debug Feature Register 0 bit functions C0, Memory Model Feature Register 0, MMFR0 To access the Debug Feature Register 0 read CP15 with9 c0, Auxiliary Feature Register Memory Model Feature Registers 10 Memory Model Feature Register 0 bit functions C0, Memory Model Feature Register 1, MMFR1 11 Memory Model Feature Register 1 bit functions 16 Memory Model Feature Register 1 format DMB C0, Memory Model Feature Register 2, MMFR2WFI 3112 Reserved C0, Memory Model Feature Register 3, MMFR313 Memory Model Feature Register 3 bit functions 14 Instruction Set Attributes Register 0 bit functions Instruction Set Attributes RegistersC0, Instruction Set Attributes Register 0, ISAR0 20 Instruction Set Attributes Register 1 format C0, Instruction Set Attributes Register 1, ISAR1 Indicates support for if then instructions C0, Instruction Set Attributes Register 2, ISAR2ITE Indicates support for PSR instructions 16 Instruction Set Attributes Register 2 bit functionsPSR Thumb instruction sets C0, Instruction Set Attributes Register 3, ISAR317 Instruction Set Attributes Register 3 bit functions 23 Instruction Set Attributes Register 4 format C0, Instruction Set Attributes Register 4, ISAR4 18 Instruction Set Attributes Register 4 bit functions C0, Instruction Set Attributes Registers12 c0, Current Cache Size Identification Register 8KB 4KB 3130 Reserved 13 c0, Current Cache Level ID Register 15 c1, System Control Register 14 c0, Cache Size Selection Register Nmfi 23 System Control Register bit functionsAFE TRE = strict alignment fault checking enabled Enables L1 data cache= data caching disabled. This is the reset value = data caching enabled 24 Auxiliary Control Register bit functions Auxiliary Control RegistersC1, Auxiliary Control Register Deolp AxiscenAxiscuen Dilsm Dnch RsdisDbwr Dlfo C15, Secondary Auxiliary Control Register 25 Secondary Auxiliary Control Register bit functions UFC DoofmacsIXC OFC Atcmecc 17 c1, Coprocessor Access RegisterPrimary input RMWENRAM1 defines the reset value Primary input RMWENRAM0 defines the reset value All other encodings for these FSR bits are Reserved Fault Status and Address RegistersC5, Data Fault Status Register To use the Dfsr read or write CP15 with C5, Instruction Fault Status Register28 Data Fault Status Register bit functions 29 Instruction Fault Status Register bit functions To access the Ifsr read or write CP15 withC5, Auxiliary Fault Status Registers There are two auxiliary fault status registers = Btcm C6, Data Fault Address Register30 Adfsr and Aifsr bit functions = Atcm 19 c6, MPU memory region programming registers C6, Instruction Fault Address Register C6, MPU Region Base Address Registers C6, MPU Region Size and Enable Registers 32 Region Size Register bit functions C6, MPU Region Access Control Registers158 Sub-region disable TEX 33 MPU Region Access Control Register bit functions 35 MPU Memory Region Number Register bit functions 34 Access data permission bit encodingC6, MPU Memory Region Number Register UNP Point of Unification PoU Cache operationsPoint of Coherency PoC Set and Way format Invalidate and clean operations 37 Widths of the set field for L1 cache sizes Size Set 37shows the cache sizes and the resultant bit range for SetAddress format 36 Functional bits of c7 for Set and Way 38 Functional bits of c7 for address format Bits Field Data Synchronization Barrier operationData Memory Barrier operation 21 c9, Btcm Region Register 39 Btcm Region Register bit functions To access the Btcm Region Register, read or write CP15 with22 c9, Atcm Region Register 40 Atcm Region Register bit functions To access the Atcm Region Register, read or write CP15 with23 c9, TCM Selection Register 24 c11, Slave Port Control Register RAZ/UNP 25 c13, Fcse PID Register26 c13, Context ID Register 312 Reserved 27 c13, Thread and Process ID Registers Ccnt overflow IRQ request C15, nVAL IRQ Enable Set RegisterValidation Registers Ccnt overflow FIQ request C15, nVAL FIQ Enable Set Register Ccnt overflow reset request C15, nVAL Reset Enable Set RegisterC15, nVAL Debug Request Enable Set Register Ccnt overflow debug request C15, nVAL IRQ Enable Clear Register 48 nVAL IRQ Enable Clear Register format C15, nVAL FIQ Enable Clear Register 303 Reserved UNP or Sbzp C15, nVAL Reset Enable Clear Register 51 nVAL Debug Request Enable Clear Register format C15, nVAL Debug Request Enable Clear Register B0000 4kB B0001 8kB B0011 16kB B0111 32kB B1111 64kB C15, nVAL Cache Size Override Register50 nVAL Cache Size Override Register 318 Reserved 53 Correctable Fault Location Register cache Correctable Fault Location Register 52 Correctable Fault Location Register cache C15, Build Options 2 Register To access the Build Options 1 Register, write CP15 withBuild Options Registers C15, Build Options 1 Register Atcmes 55 Build Options 2 RegisterNoicache Nodcache Nompu BtcmesNoie Nofpu Axibusparity To access the Build Options 2 Register, write CP15 withNoharderrorcach Dcachees Prefetch Unit About the prefetch unit Disabling program flow prediction Branch prediction Incorrect predictions and correction Configuring the branch predictorBranch predictor Return stack Events and Performance Monitor Event Bit position Update ValueAbout the events Event bus interface bit functions ETMEXTOUT1 ETMEXTOUT0 Dual issue case B1, B2, F2 load/store, F2D Non-cacheable access on AXI master busInstruction cache access But with different attributes Dual issue case a branch TCM correctable ECC error reported by prefetch unit Yes TCM correctable ECC error reported by load/store unit Yes About the PMU 2shows how the bit values correspond with the Pmnc Register Performance monitoring registersPerformance monitoring registers are described 1 c9, Performance Monitor Control Register Pmnc Register bit functions 2 c9, Count Enable Set Register Cntens Register bit functions Bits Field Function To access the Cntens Register, read or write CP15 with3 c9, Count Enable Clear Register Cntenc Register bit functions Bits Field Function To access the Cntenc Register, read or write CP15 withCycle counter enable clear 4 c9, Overflow Flag Status Register 5 c9, Software Increment Register To access the Flag Register, read or write CP15 with5shows how the bit values correspond with the Flag Register 313 Reserved RAZ on reads, Sbzp on writes Increment Counter To access the Swincr Register, read or write CP15 with6 c9, Performance Counter Selection Register Swincr Register bit functions Bits Field Function SEL 7 c9, Cycle Count Register8 c9, Event Selection Register EVTSELx Register bit functions To access the EVTSELx Register, read or write CP15 with Useren Register bit functions 10 c9, User Enable Register9 c9, Performance Monitor Count Registers 10 Intens Register bit functions Bits Field Function 11 c9, Interrupt Enable Set RegisterCcnt overflow interrupt enable 11 Intenc Register bit functions Bits Field Function 12 c9, Interrupt Enable Clear RegisterCcnt overflow interrupt enable bit To access the Intenc Register, read or write CP15 with Use of the event bus and counters Event bus interface Memory Protection Unit MPU faults onMPU software-accessible registers on True Default memory mapAbout the MPU Subregions Memory regionsRegion base address Region size Region Region access permissionsRegion attributes Overlapping regions Example of using subregions Example of using regions that overlap TCM regions Background regions Memory types Using memory types ARM DDI 0363E TEX20, C, and B encodings Description Memory Type Shareable? Region attributes 1BB Cacheable memory policies Following code is an example of disabling the MPU On page 7-2shows the default memory mapMPU interaction with memory system Permission fault MPU faultsBackground fault Permission fault Alignment fault Background fault On page 4-5shows the CP15 registers that control the MPU MPU software-accessible registers Level One Memory System About the L1 memory system L1 memory system block diagram Parity About the error detection and correction schemesParity Bit ECC on Read-Modify-Write Error checking and correctionHard errors Bit ECC Correct-and-retry Error correctionCorrect inline MPU faults Fault handlingFaults Classes of fault that can occur are TCM external faults External faultsCache and TCM parity and ECC errors Abort exceptions Fault status informationDebug events Precise and imprecise aborts Usage models Precise abort exceptionsImprecise abort exceptions AXI Correctable errorsTypes of aborts Conditions Source Precise Fatal ARM DDI 0363E TCM attributes and permissions About the TCMs Handling TCM parity errors on Handling TCM ECC errors on Atcm and Btcm configurationTCM internal error detection and correction TCM arbitration Handling TCM parity errorsHandling TCM ECC errors TCM port protocol External TCM errorsTCM initialization AXI slave interfaces for TCMs Store buffer About the caches Store buffer draining Cache maintenance operationsStore buffer merging Store buffer behavior Error build options Cache error detection and correction Cache parity error behavior Value Behavior Address decoder faultsHandling cache parity errors Cache ECC error behavior Value Behavior Handling cache ECC errors Errors on evictions Errors on instruction cache readErrors on data cache read Errors on data cache write Invalidate all instruction cache Clean data cache by set/way Tag RAM Cache RAM organizationTag RAM Dirty RAM on Data RAM on Organization of a dirty RAM line Dirty RAMData RAM Cache sizes and tag RAM organization Tag RAM organization Nonsequential read operation performed with one RAM access Data RAM sizes without parity or ECC implemented 13 Data cache RAM bits, with parity Description 15 Data cache data RAM sizes with ECC Cache size Data RAMs Cache interaction with memory systemDisabling or enabling all of the caches Following code is an example of enabling caches Disabling or enabling data cache Disabling or enabling error checkingDisabling or enabling instruction cache MCR p15 R0, c1 Write System Control Register Internal exclusive monitor Memory types and L1 memory system behavior Data-cache error events Error detection eventsTCM error events Instruction-cache error events ARM DDI 0363E Level Two Interface About the L2 interface Attribute Value Comments AXI master interface1shows the AXI master interface attributes Write response Identifiers for AXI bus accessesOutstanding write/read access on different IDs Outstanding write accesses with the same ID Aruserm and Awuserm encodings Eviction bufferMemory attributes Arcachem and Awcachem encodings Encoding a Meaning Memory system implications for AXI accesses Linefills on AXI master interface transfersStrongly Ordered and Device transactions on Address20 Restrictions on AXI transfersStrongly Ordered and Device transactions Non-cacheable Ldrb Ldrh from Strongly Ordered or Device memory Address30 LDR or LDM that transfers one register LDM5, Strongly Ordered or Device memory Address40 LDM that transfers five registers Strh to Strongly Ordered or Device memory Address20 Strb to Strongly Ordered or Device memory Address40 First Wstrbm STR or STM of one registerSTM of seven registers Non-cacheable reads LinefillsCache line write-back eviction 15 LDR or LDM1 from Non-cacheable Normal memory Address20 14 Ldrh from Non-cacheable Normal memory Address20 Non-cacheable or write-through writes AXI transaction splitting 20 AXI transaction splitting, data in two cache lines Normal write merging Example 9-1 Write merging ARM DDI 0363E AXI slave interface for cache RAMs AXI slave interface AXI slave control TCM parity and ECC supportCache parity and ECC support 25 AXI slave interface attributes AXI slave characteristics Enabling or disabling AXI slave accesses 26 RAM region decode AxUSERS bit One-hot RAM select Accessing RAMs using the AXI slave interfaceTCM RAM access on Cache RAM access on RAM selected TCM RAM accessARADDRSMSB, see Table 27 TCM chip-select decode Btcm ports This section contains the following Cache RAM accessMemory map when accessing the cache RAMs 0001 Bank 0010 0100 1000 Data RAM access0010 Bank 0100 1000 31 Cache data RAM bank/address decode Inputs ARADDRS1815 35 Data format, data cache, with ECC Data bit Description 34 Data format, instruction cache, with ECC Tag RAM access ARM DDI 0363E 43 Dirty register format, with ECC Data bit Description Dirty RAM access ARADDRS1815 = 4b1111 Other examples of accessing cache RAMs About power control on Power management on Power Control About power control Shutdown mode Run modeStandby mode Dormant mode Communication to the Power Management Controller Debug state on Cache debug on Debug Protocol converter Debug systemsDebug host Protocol converter Debug target Debug host Programming the debug unit About the debug unitHalting debug-mode debugging Monitor debug-mode debugging All other state information associated with the debug unit Coprocessor registers summary 11.3.2 CP14 access permissionsDebug register interface Coprocessor registers Debug memory-mapped registers Offset Register Access Mnemonic Description Hex NumberMemory-mapped registers Instruction Mnemonic Description Memory addresses for breakpoints and watchpoints Privilege of memory access permission Power domainsEffects of resets on debug registers APB port access permissions Other registers External debug interface access permissions RegistersLock Other Debug registers 11.4.2 CP14 c0, Debug ID Register Accessing debug registersDebug register descriptions 6shows the CP14 debug register map BRP Debug ID Register functionsWRP 11.4.4 CP14 c0, Debug Self Address Offset Register To use the Debug ID Register, read CP14 c0 with11.4.3 CP14 c0, Debug ROM Address Register To use the Debug ROM Address Register, read CP14 c0 with Debug Self Address Offset Register functions Debug Self Address Offset Register format 10 Debug Status and Control Register functions 11.4.5 CP14 c1, Debug Status and Control Register Flag is set to 1 on entry to debug state ARM Execute ARM instruction enable bit= disabled, this is the reset value MOE DTR access mode Data Transfer Register Reserved RAZ Watchpoint Fault Address Register12 Watchpoint Fault Address Register functions Vector Catch Register SVC 14 Debug State Cache Control Register functions Bits Field Reset Description ValueDebug State Cache Control Register Instruction Transfer Register 315 Reserved Debug Run Control Register15 Debug Run Control Register functions Breakpoint Control Registers Breakpoint Value Registers 17 Breakpoint Control Registers functions BVR2220 Meaning +0 is accessedCorresponding instruction address breakpoint 18 Meaning of BVR bits 19 Watchpoint Value Registers functions Bits Description Watchpoint Value RegistersWatchpoint Control Registers 20 Watchpoint Control Registers functions 11 Watchpoint Control Registers format Operating System Lock Status Register Accessed 21 OS Lock Status Register functions Authentication Status Register 23 Prcr functions Device Power-down and Reset Control RegisterDevice Power-down and Reset Status Register = Dbgnopwrdwn is LOW. This is the reset value 24 Prsr functions 15 Prsr format Processor ID Registers Management registers 27 Claim Tag Set Register functions Bits Field Function Claim RegistersClaim Tag Set Register Lock Status Register Lock Access Register318 Reserved RAZ or Sbzp Claim tag clear Reset value is Claim Tag Clear Register 30 Device Type Register functions Device Type RegisterDebug Identification Registers Bits Value Description 32 Fields in the Peripheral Identification RegistersField Size Description 33 Peripheral ID Register 0 functions 37 Peripheral ID Register 4 functions 34 Peripheral ID Register 1 functions35 Peripheral ID Register 2 functions 36 Peripheral ID Register 3 functions 1022 1020Component Identification Register 1021 Software debug event Debug events Watchpoint debug events Halting debug eventBehavior of the processor on debug events Debug event priority Debug exception Four CP15 registers that record abort information are 40shows the values in the link register after exceptionsFollowing sections describe Effect of debug exceptions on CP15 registers and Wfar Avoiding unrecoverable states 41 Read PC value after debug state entry Debug statePrivilege on Entering debug state 41 Read PC value after debug state entry Debug event Behavior of the PC and Cpsr in debug state Privilege Accessing registers and memoryExecuting instructions in debug state Writing to the Cpsr in debug state Exceptions in debug state Coprocessor instructionsEffect of debug state on non-invasive debug Effects of debug events on processor registers Leaving debug state Precise Data abortImprecise Data Abort Imprecise Data Aborts on entry and exit from debug state Sets the DSCR1 core restarted flag to Cache coherency in debug state Cache debugThis section describes cache debug. It consists Cache pollution in debug state External debug interface APB signalsMiscellaneous debug signals This section describes the miscellaneous debug signals Non-invasive debug permitted Authentication signalsChanging the authentication signals 42 Authentication signal restrictions Dbgen a Issue an Instruction Synchronization Barrier ISB instruction Example 11-1 Executing an ARM instruction through the ITR Using the debug functionality Debug communications channel Rules for accessing the DCC Example 11-4 Target to host data transfer host end Software access to the DCCDebugger access to the DCC Example 11-5shows the code for host-to-target data transfer Example 11-6 Polling the DCC host end Programming breakpoints and watchpointsThis section describes the following operations Programming simple breakpoints and the byte address select Example 11-7 Setting a simple breakpoint Setting a simple aligned watchpoint Example 11-8 Setting a simple aligned watchpoint Setting a simple unaligned watchpoint Not required Example 11-9 Setting a simple unaligned watchpoint45shows some examples Single-stepping Example 11-11 Entering debug state Debug state entryExample 11-10 Single-stepping off an instruction Example 11-12 Leaving debug state Debug state exit Example 11-13 Reading an ARM register Accessing registers and memory in debug stateThis section describes the following Reading and writing registers through the DCC Example 11-16shows the code for reading the Cpsr Reading the PC in debug stateExample 11-15shows the code to read the PC Reading the Cpsr in debug state Example 11-17 Writing the Cpsr Example 11-19 Checking for an abort after memory accessReading memory Example 11-18shows the code for reading a byte of memory Example 11-21 Reading a word of memory Example 11-20 Reading a block of bytes of memory Fast register read/write Example 11-22 Changing the DTR access modeExample 11-23 Reading registers in stall mode Example 11-24 Writing registers in stall mode Example 11-25 Reading a block of words of memory Fast memory read/write Example 11-27 Reading a coprocessor register Accessing coprocessor registers 11-70 Debugging systems with energy management capabilities Emulating power down 11-72 FPU Programmer’s Model About the VFPv3-D16 architecture About the FPU programmer’s modelFPU functionality FPU views of the register bank General-purpose registers 1shows the VFP system registers in the Cortex-R4F FPU System registersVFPv3 architecture describes the following system registers This is a change in VFPv3 compared to VFPv2 All hardware ID information is privileged access onlyFpsid is privileged access only Mvfr registers are privileged access only Rmode Floating-Point Status and Control Register, FpscrFpscr Register bit functions DNM DNM IXE RAZ UFE OFE DZE IOE IDC Floating-Point Exception Register, FpexcLEN IDE RAZ MVFR0 Register bit functions Media and VFP Feature Registers, MVFR0 and MVFR1Floating-Point Exception Register bit functions DEX Full denormal arithmetic supported for VFP MVFR1 Register bit functions Default NaN mode Full-compliance mode Flush-to-zero mode Default NaN modeFull-compliance mode Flush-to-zero mode NaN handling Compliance with the Ieee 754 standardComplete implementation of the Ieee 754 standard Ieee 754 standard implementation choices CDP ComparisonsUnderflow QNaN and SNaN handling Exceptions Integration Test Registers About Integration Test Registers Programming and reading Integration Test Registers Software access using APB Itmiscin Register ItctrlItetmif Itmiscout 1110 Processor integration testing1312 Performing integration testing Using the Integration Test Registers Itetmif Register bit assignments Bits Name Function Itetmif Register ETM interface Itmiscout Register bit assignments Bits Name Function Itmiscout Register Miscellaneous OutputsItmiscin Register Miscellaneous Inputs Etmextout Integration Mode Control Register ItctrlBits Name Function Dbgrestart Intmode Bits Access Reset value Name Function7shows the fields of the Itctrl Register RAZ/SBZP Multiplies on Divide on Branches on Cycle Timings and Interlock Behavior Dual issue on Instruction execution overview About cycle timings and interlock behavior Definition of terms Following sequence where R1 is a Late Reg takes two cyclesFlag-setting instructions Conditional instructions Assembler language syntax Takes three cycles because of the result latency of R1 Register interlock examplesInstruction Behavior Sequence Takes two cycles because there are no register dependencies Cycle counts if destination is the PC Data processing instructionsCycle counts if destination is not PC Register controlled shifts Example interlocksShifter QADD, QDADD, QSUB, and Qdsub instructions SEL Media data-processing USAD8 instruction Sum of Absolute Differences SADInstruction sequence Behavior Result of the USAD8 instruction Umlals Multiplies 14-13 Divide Example instruction Cycles Memory Comments Branches10 Branch instruction cycle timing behavior All MSR instructions to the Spsr Mode changingProcessor state updating instructions All MRS instructions 13shows the cycle timing behavior for loads to the PC Single load and store instructions Example instruction Cycles Memory Result Comments Latency Base register update13 Cycle timing behavior for loads to the PC 14-19 Load and Store Double instructions Register offset, then 3-issue cycles Write-back Load and Store Multiple instructions Correct condition prediction and incorrect Load Multiples, where the PC is in the register listCorrect condition prediction and correct Return stack prediction 14-23 RFE and SRS instructions Clrex Synchronization instructions Some instructions such as cache operations take more cycles Coprocessor instructions Prefetch Abort Undefined Instruction SVC formerly SWI Miscellaneous instructions Serializing Floating-point register transfer instructionsBlocking and serializing 2,2 Floating-point load/store instructionsBit aligned address Not aligned 4,5 2,3 Floating-point single-precision data processing instructions Floating-point double-precision data processing instructions Dual issue rules Dual issueDual issue rules Permitted combinations on 28 Permitted instruction combinations Dual issue First instruction Second instruction CasePermitted combinations Case F2Db Case F2stbAny single-precision CDPi, excluding Multiply-accumulate instructionso Processor timing on Processor timing parameters on AC Characteristics Processor timing Clock uncertainty 50% Processor timing parametersInput port timing parameters Clock uncertainty 10% Clock uncertainty 60% 3shows the timing parameters for the interrupt input ports4shows the input timing parameters for the AXI master port Rreadys 5shows the input timing parameters for the AXI slave port 7shows the input timing parameters for the ETM input ports 6shows the input timing parameters for the debug input ports Clock uncertainty 40% 8shows the timing parameters for the test input portsClock uncertainty 65% 11shows the timing parameters for the interrupt output ports Output ports timing parameters Write response channel Clock uncertainty 60% 13shows the timing parameters for the AXI slave output ports BRESPS10 Clock uncertainty 45% 16shows the timing parameters for the test output ports Fpidc 18shows the timing parameters for the FPU output signals 15-13 FPU signals on page A-23 Processor Signal Descriptions From any clock About the processor signal descriptionsAny Signal Direction Clocking Description Global signalsTable A-1 Global signals Information Configuration signalsTable A-2shows the processor configuration signals Table A-2 Configuration signals Tie High for odd parity Tie LOW for even parity RMWENRAM10b Interrupt signals, including VIC interface signals AXI master port L2 interface signalsTable A-4 AXI master port signals for the L2 interface Protection signals provide addition information about a bus Identification tag for the write data group of signalsIdentification tag for the write response signal Identification tag for the read address group of signals AXI slave port AXI master port error detection signalsTable A-5 AXI master port error detection signals Table A-6 AXI slave port signals for the L2 interface One to 16. a four bit binary value minus one determines Protection information, privileged/normal access. AWPROT0AXI specification Protection information, privileged/normal access. ARPROT0 Table A-7 AXI slave port error detection signals AXI slave port error detection signalsATCM, one hot. AWUSERS30 signal is not part Standard AXI specification Table A-9shows the B0TCM port signals TCM interface signalsTable A-8shows the Atcm port signals = DMA Table A-10shows the B1TCM port signalsTable A-10 B1TCM port signals Write parity or ECC code for B1TCM B1TCM RAM access is sequentialAddress for B1TCM data RAM Write data for B1TCM data RAM Table A-11 Dual core interface signals Dual core interface signalsTable A-11shows the dual redundant core interface signals Table A-12 Debug interface signals Debug interface signalsTable A-13shows the debug miscellaneous signals Input Tie-off Debug self-address offset valid Table A-13 Debug miscellaneous signalsInput Tie-off Debug ROM physical address valid Input Tie-off Debug self-address offset Table A-14 ETM interface signals ETM interface signalsTable A-14shows the ETM interface signals Table A-15 Test signals Test signalsTable A-15shows the test signals Table A-16shows the Mbist signals Mbist signals Table A-17shows the validation signals Validation signals Table A-18 FPU signals FPU signals ECC scheme selection guidelines on page B-2 ECC Schemes ECC scheme selection guidelines Clarified little-endian format NCPUHALT removed from timing diagram Added sectionsRevisions Clarified byte-invariant big-endian format Change Location Table C-1 Differences between issue B and issue C No technical changes Table C-2 Differences between issue C and issue D Base register write-back GlossaryAbort, and an internal or External Abort See also Data Abort, External Abort and Prefetch Abort See Advanced Microcontroller Bus Architecture See also Advanced High-performance BusSee Advanced High-performance Bus That are divisible by four and two respectively Completed transfer Active read transactionActive transfer Active write transaction Write ID width Read ID widthRead issuing capability Write ID capability See also Beat See also Burst Bus Accesses are expected to be word-alignedAccessed in parallel during a cache look-up See also Word-invariant See also Dirty See also Clean See Embedded Trace Macrocell Precision and the fraction is all zeros An instruction that is architecturally UndefinedBy individual implementations Option chosen does not affect software compatibility Result of attempting to access invalid instruction memory Serviced while normal program execution is suspendedSee also Halt mode See Cold reset See Boundary scan chain Or equal to 1 and is not restricted to being a power of twoSee Should Be One See Should Be Zero User trap handler is executed See Debug test access portIncrement of +2 Destination precision A processor Expected behavior for an unaligned accessBit for the exception is set Processor-specific. a victim is also known as a cast out Cache terminology diagram